Ultra short wave system



Nov. 29, 1949 c} H. BROWN 2,489,855

' ULTRA SHORT WAVE SYSTEM Filed Nov. 1. 1945 I 47 mztizl INVENTOR (Ax/(1:: JAdW/Y.

ATTORNEY Patented Nov. 29, 1949 Charles H. Brown. Baldwin, N.

Radio Corporation of America,

of Delaware Y., assignor to a corporation Application November 1, 1945, Serial No. 626,139

v Claims. (Cl; 32-49) This invention relates to electron discharge devices and circuits therefor, for use particularly with ultra short waves below five meters, and is a continuation-in-part of my copending application Serial No. 391,063, filed April 30, 1941, ngw U. S. Patent 2,393,284, granted January 22, l 46.

.An object of the present invention is to provide an electron discharge device arrangement employing a cavity resonator as a frequency controlling element, in which waves are produced whose instantaneous wavelengths are modulated by the signal to be transmitted.

A description of the invention follows in con junction with a drawing, whose single figure l1- lustrates an embodiment of the invention.

The drawing shows a scheme for obtaining frequency or phase modulated waves at ultra short wavelengths below one meter from a cavity resonator. Element 40 represents a cavity resonator of suitable dimensions, resonate at a frequency preferably below one meter, let us say, for example, at a frequency in the range between 5 centimeters and 30 centimeters. In the interior of the resonator and suitably spaced apart from each other are a pair of dipole antenna elements 4|, 42 coupled respectively by way of lines 43 and 44 to the output and input of an oscillator 45 located externally of the resonator. Obviously, other coupling elements than dipoles can be used, such as circular loops. This oscillator is preferably mounted on the resonator to conserve space. A pair of leads 46 extend to a suitable load or utilization circuit. If desired, a suitable limiter may be coupled to leads 46 to insure a constant amplitude of oscillations in the output. By suitably spacing the dipole elements from the ends of the resonator 40, the resonator will be driven by the oscillator and resonate at the frequency determined by its dimensions.

According to the invention, it is proposed to vary these dimensions and also the resonant frequency of the resonator in accordance with signal modulations, as a consequence of which the frequency of oscillations of the oscillator 45 will vary. In this way it is possible to obtain from leads 46 waves modulated as to frequency in accordance with signal modulations. One way of varying the dimensions of the resonator 40 is to and designed to tube having input and output electrodes, a cavity.

r to thereby vary the resonator and coupled to the field in said resoits'input coupled to make oneend' wall 48 of the resonator movable in response to voice currents. It should be understood, of course, that end wall 48-is directly connected by contact with the side walls of the resonator. To achieve this, the movable end'wail may include or consist of a magnetic diaphragm which is controllable by a solenoid 49, in turn coupled to the microphone 41. If desired, the stationary solenoid may be replaced by a moving coil scheme mounted in a magnetic field, the moving coil being responsive to the voice'currents. This coil can be arranged in the air gap of a permanent or an electromagnet. It will thus be seen that the ultra high frequency field within the resonator 40 will be modulated at an audio frequency rate. poles' 4| and 42 need not be critical, although certain spacings will give better results than others. It will also be found that there will be maximum efficiency for certaincspacings to be determined by trial and error between the dipoles and the end walls.

By way of analogy only, the system of the invention can be compared to an oscillator having feed back between input and output circuits through a crystal filter.

By pre-emphasis (that is, making the relative amplitude of the higher modulation frequencies greater than they are normally) it is possible to obtain a modulation in the output to the load which is phase modulation. This can beaccomplished by using a pre-emphasis circuit in the amplifier between microphone 41 and solenoid 49.

'- What is claimed is:

1. A modulating system comprising a-vacuum resonator having a movable, wall, individual elements within and spaced from said cavity resonator and coupling said input and output electrodes respectively to said cavity resonator, and means for varying the position of said wall tuning of said cavity resonator in accordance with modulating potentials.

2. A modulating system comprising a cavity resonator, a pair of spaced coupling elements in the interior of and spaced from said cavity nator, a vacuum tube having one coupling element and its output coupled to the other coupling element, whereby said cavity resonatorforms a frequency selective feed back circuit, and means for varying the volume of said cavity resonator in accordance with modulating potentials.

3. A modulating system comprising a cavity resonator having a resonance frequency corresponding to a wave smaller than one meter,

a movable diaphragm in one wall thereof, a coil or controlling the movement of said diaphragm,

The distance between the dian audio frequency modulating system coupled or said resonator, one dipole or which is adjato said coil, and an oscillator having a feedback cent said one end wall and the other dipole of circuit controlling the frequency of oscillations which is adjacent an opposite wall or said resooi' said oscillator, said feedback circuit includnator, an oscillator having its input coupled by a ing input and output circuits coupled to spaced 5 pair of leads to one dipole and its output coupled probes in the interior of said resonator. by another pair of leads to the other dipole, a

4. A'modulating system comprising a cavity utilization circuit coupled to one oi! said pair oi resonator resonant at an ultra high frequency leads, and means for controlling the movement of thereof, a pair oi. spaced dipoles in the interior 10 time CHARLES H; BROWN.

REFERENCES CITED other dipole, a utilization circuit coupled to the e f n r r f r h output of said oscillator, and means for con-'llg z g M e o rem d m t e trolling the movement of said diaphragm in respouse to signal od mu UNITED STATES PATENTS 5. A modulating system comprising a cavity p b r Name Date resonator resonant at an ultra high frequency 2,174,701 Koch Oct. 3, 1939 and having a movable diaphragm in one end wall 2,281,935 Hansen et a1. May 5, 1942 thereof, a pair oi spaced dipoles in the interior 2,312,919 Litton Mar. 2, 1943 

